That's because they kept it in secret, and it was presented, on the 34th anniversary of Islamic Revolution, by Ahmadinejad, how Radio Television of Serbia told.

My personal opinion: Plane looks great and I would never expect something like this from Iran, it's really futuristic looking. Only thing is it's specifications- maneuverability, armament, etc. We'll wait for it's first demonstrations in air, but I have no doubt in this plane.

1. They claim the plane is stealth yet a clear canopy and downward sloping wings create huge radar returns
2. They say it is supersonic, yet the airspeed indicator only goes to 300 knots
3. The ejection seat looks to be right out of a MIG
4. The air intakes are way too small for newer generation engines and there is no thrust vectoring. There aren't even any propelling nozzles
5. The nose is too small for radar instruments
6. Small wings means low fuel capacity and terrible range, also means large turning radius at faster speeds. If they use external fuel tanks, that ruins stealth
7. All the cockpit parts are off-the-shelf parts, many of which have English labeling, and none of them are even wired up
8. No weapons or targeting screens
9. No airspeed/vert airspeed/altimeter pitots
10. Huge gaps in hinges and control surfaces which ruin stealth
11. Too small for internal weapons, which means no stealth ability

All in all, the plane is just a cheap model but it fooled you guys just fine.

1. CommanderDef already pointed it out.
2. CommanderDef already pointed it out. Just because it's looks like a random airspeed indicator doesn't mean it's the same one.
3. Do some research. It looks nothing like a Zvezda ejection seat.
4. We have yet to see the engine and a nozzle may be part of that engine. The engine is calmed to be made 100% in Iran so keeping it classified dose make sense. And the intake are overall as big as that of the Chinese FC-1.
5. Depends on the size of radar. There are BVR radars that are smaller than my head.
6. This fighter is likely a point/territorial defense fighter akin to Mig-29, so range is irrelevant.
8. Obviously, as it's a mock-up made for an international press release.
9. It is likely the original prototype aircraft has a helmet mounted display, Iran's been making them for quite some time now.
10. I have no idea what "gaps" are you speaking about that is going to ruin stealth.
11. The intake are on top, so there are place for at least two small weapons bey under the belly.

In short, you whoever you are need to do some actual research rather than copy pasting from militaryphotos.com and other places.

I gotta say I really can't see "5th generation" in any of this. CommanderDef, since when do you need to see an airspeed indicator in high quality? Even from the picture you can tell the indicator has a ridiculously small amount of increments.

If I recall correctly the Fulcrum is an extremely fast response jet, meant to hold the line until the Flankers arrive. Hardly a job fitting for a 5th gen stealthy. What are are they going to do? Throw all 10 jets (or however many they have by 2080, mass producing 5th Generation stealth fighters is quite a task) to hold off the attacking force? If they have to fill the rapid response gap with non-stealth attack jets for joint defense then doesn't that almost completely nullify the surprise advantage of the F-313?
Anyway, all in all, there is absolutely no way on this planet that Iranian defense contractors could have come up with a completely indigenous 5th gen stealth jet prototype already. You don't have to have any brains whatsoever to see that.
This is nothing but a propaganda model, and like Guest said, it fooled you guys just fine.

I too now doubt it's actually a 5th gen. It's likely a Gen 4+ fighter, intended to replace the aging F-5 or just another test bed. It's calmed to have simple to built and those bent wing means it may not need extensive fly-by-wire or other advance technology (Or any at all) to use it effectively. And if that so, it won't be such difficult to built in large numbers. As for it's stealth capability, the design is definitely will have reduced RCS and they may utilized some RAM in it (Simple RAM's aren't exactly a hard to get or built stuff nowadays). The stealth feature of this plane is likely secondary, featured to make sure that enemy (4th gen fighter like F-15/16/18 and maybe the JSF) have a difficult time locking on with radar guided missile so the the F-313 pilots can engage them in visual range dogfights, where this plane will truly have an advantage as it seem to optimized for extreme maneuverability.

Iran is making Bavar 373 SAM along with a low-band radar to counter the F-22, the F-313 is likely designed to have an upper hand over conventional fighter.

This is definitely not 5th generation. I'd be surprised if it could even fly. If you get a good look at the engine, you'll notice that there is no nozzle! The entire plane will melt if they actually turn it on. Also, if it's "one of the best fighters in the world" why doesn't it have a HUD? That's right, look at internal pictures of the cockpit, and you'll see what I'm talking about. Also, the video that shows the plane allegedly flying is clearly a remote controlled toy. Notice how it wobbles from side to side during flight. And finally, common sense dictates that Iran cannot developed a 4+ generation fighter, let alone a 5th generation one. Russia and China are struggling to produce AESA radars and perfect stealth technology, how did Iran cook this up in spite of all the sanctions leveled against it? That just isn't possible.

On your last point, it's something called "stealing high tech stuff from others"

oh and before you say something along the lines of "it's not possible to build something good simply by relying on stealing high tech" well, than we have to face the impossible possility that the J-20 was acutally developed and not just stolen (and we all "know" that the Chinese are not capable of building anything other than cheap Walmart goods and cold war era weapons).

So which is it? The Iranians are not as stupid as FoxNews would like you to believe, or that it is possible to be competitive simply by stealing other countries' tech?